The display manner of an electroluminescence display device such as an organic light-emitting diode (OLED) display is different from that of a conventional liquid crystal display. Since backlight is not needed in an OLED display, the OLED display device can be made lighter, thinner and with a greater viewing angle, and can significantly save energy, thus the OLED display technology becomes more and more popular.
An OLED display includes a driving circuit and an OLED light-emitting device. Electric current is outputted through the driving circuit to drive the light-emitting device to emit light with different luminance. FIG. 1 shows the pixel structure of an OLED display in the prior art. As shown in FIG. 1, an OLED pixel in the prior art includes a first signal line CN1, a second signal line CN2, a driving circuit and an OLED light-emitting device, wherein the driving circuit comprises a capacitor Cst, a driving transistor T1, a second transistor T2, a third transistor T3 and a fourth transistor T4. The capacitor Cst is connected in series between the gate and source of the driving transistor T1, the third transistor T3 and the fourth transistor T4 is connected in series between the gate and drain of the driving transistor T1, the drain of the driving transistor T1 is connected to the source of the second transistor 12, the first signal line CN1 is respectively connected to the gate of the third transistor T3 and the gate of the fourth transistor T4, and the second signal line CN2 is connected to the gate of the second transistor T2. The driving circuit receives an external input data current Idata which will be stored in the capacitor Cst, and then the capacitor Cst generates driving current Ioled driving OLED to emit light, the data current Idata in the prior art being equal to the driving current Ioled. Since the driving current Ioled required when OLED emits light is relatively lower, the data current Idata is also relatively lower. When the capacitor Cst is relatively large, it takes a longer time for a relatively low data current Idata to charge the capacitor Cst, and in the case of a low data current Idata, the charging time of the capacitor Cst will be very long, resulting in a slow refresh rate of the OLED display.